I had to go to the ER a couple of times, and have a bunch of depersonalization episodes that were really horrific. Then I quit, and thought I was gonna die of withdrawals and had to get on meds to lower my blood pressure and calm my tremors.
That's what it took for me. I wish I had the proper motivation or whatever before, but even waking up every day wishing I would quit, I was back at it in a mere few hours. This went on for years. I don't know what the answer is, sadly. I guess it just wasn't bad enough yet.